Studies on non-enzymatic browning of glucosamine and glucosamine-amino acid solutions

• Author / Creator

  Dhungel, Prinjiya

• Non-enzymatic browning reactions represent a complex phenomenon occurring during thermal processing of food, and are categorised as either the Maillard reaction or caramelization. Besides temperature, these reactions depend upon water activity (aw), pH and the concentration of reactants. Non-enzymatic browning reactions give flavour and colour to foods, and are central in the production of caramel colours. On the other hand, these reactions also produce potential toxic compounds such as 4-methylimidazole (4-MEI), 5-hydroxymethylfurfural (5-HMF) and 2-acetyl-5-tetrahydroxybutyl imidazole (THI) which increase with temperature and are defined as neo-formed contaminants in caramel.
  Glucosamine (GlcN) is an aminosugar capable of eliciting non-enzymatic browning reactions even at 25-37°C. The structure of GlcN is peculiar as it contains both an amino group and a carbonyl group in the same compound; this makes it an unstable molecule capable of forming degradative and self-condensation reactions generating plethora of compounds. One compound generated by the non-enzymatic browning of GlcN is diacetyl, and is known for its appealing butter-like aroma. Other compounds are fructosazine (FR) and deoxyfructosazine (DOFR), and are known for anti-diabetic and anti-inflammatory properties, and glyoxal, methylglyoxal, diacetyl and 3-deoxyglucosone for antimicrobial properties. Thus, GlcN can be used to produce a caramel containing interesting functional compounds with aromatic, antimicrobial and anti-inflammatory properties even at moderate temperatures. Hence, one of the main objectives of this thesis was to produce safe and flavourful GlcN-derived caramel under vacuum conditions (“sous-vide”) or by combining with specific amino acids.

  The first study was designed to study the sous-vide non-enzymatic browning of GlcN at 50, 60 and 70°C for 12 h. The physico-chemical properties, quantification of α-DCs, polyhydroxylalkyl pyrazines (FR and DOFR), alkylimidazoles (4-MEI and THI) and 5-HMF were determined in the sous-vide GlcN caramels as compared to GlcN caramels generated under the normal, ambient oxidative conditions. The results revealed that caramelization under vacuum generated significantly lower (p < 0.05) diacetyl concentrations compared to oxidative conditions at all incubation temperatures. Significantly greater concentrations of FR were found in the vacuum treatments. THI and 5-HMF concentrations in all caramels studied were well below the toxicity levels, while the potentially more toxic 4-MEI was not detected in any of the caramels produced. This study shows that sous-vide conditions did not improve the formation of butterscotch flavour but increased the amount of the biologically active polyhydroxylalkyl pyrazines.
  The second study focused on investigating the effect of different amino acids on non-enzymatic browning of GlcN incubated at 70°C for 12 h. The resulting GlcN-amino acid “caramels” were analyzed for α-DCs, polyhydroxyalkyl pyrazines, heterocyclic compound and alkylimidazoles. The greatest (p < 0.05) amount of butterscotch aromatic compound diacetyl, and FR and DOFR were generated in GlcN-glycine caramels. GlcN-arginine caramels generated the greatest (p < 0.05) amount of HMF. The neo-formed contaminants alkylimidazoles (4-MEI and THI) were not present in any of the GlcN-amino acid caramels. The THI was present in the GlcN control, suggesting that the addition of the amino acids completely inhibited the formation of these contaminants. Principal component analysis categorised the majority of the GlcN-amino acid combinations where GlcN-glycine and GlcN-serine were the best discriminated. In general, the addition of glycine to GlcN non-enzymatic browning produces a “caramel” solution with the greatest concentration of flavourful compounds.
  Overall, this thesis demonstrated that different types of caramels produced depend on the presence or absence of vacuum, as well as the type of amino acids added during the non-enzymatic browning reaction of GlcN. These caramels have the potential to be used in different food applications such as simple colourants, as aromatic caramels, or even conferring beneficial health activities.

• Subjects / Keywords

  • Glucosamine
  • Non-enzymatic browning
  • Sous-vide

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3MG7GB63

• License

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